Creating Your First Yii Application
===================================

To give you an initial experience with Yii, in this section we describe how to
create your first Yii application. We will use `yiic` (command line tool)
to create a new Yii application and `Gii` (powerful web based code generator)
to automate code creation for certain tasks. For convenience,
we assume that `YiiRoot` is the directory where Yii is installed, and `WebRoot`
is the document root of our Web server.

Run `yiic` on the command line as follows:

~~~
% YiiRoot/framework/yiic webapp WebRoot/testdrive
~~~

> Note: When running `yiic` on Mac OS, Linux or Unix, you may need to
> change the permission of the `yiic` file so that it is executable.
> Alternatively, you may run the tool as follows,
>
> ~~~
> % cd WebRoot
> % php YiiRoot/framework/yiic.php webapp testdrive
> ~~~

This will create a skeleton Yii application under the directory
`WebRoot/testdrive`. The application has a directory structure that
is needed by most Yii applications.

Without writing a single line of code, we can test drive our first Yii
application by accessing the following URL in a Web browser:

~~~
http://hostname/testdrive/index.php
~~~

As we can see, the application has four pages: the homepage, the about page,
the contact page and the login page. The contact page displays a contact
form that users can fill in to submit their inquiries to the webmaster,
and the login page allows users to be authenticated before accessing privileged
contents. See the following screenshots for more details.

![Home page](first-app1.png)

![Contact page](first-app2.png)

![Contact page with input errors](first-app3.png)

![Contact page with success message](first-app4.png)

![Login page](first-app5.png)


The following diagram shows the directory structure of our application.
Please see [Conventions](/doc/guide/basics.convention#directory) for a detailed
explanation.

~~~
testdrive/
   index.php                 Web application entry script file
   index-test.php            entry script file for the functional tests
   assets/                   containing published resource files
   css/                      containing CSS files
   images/                   containing image files
   themes/                   containing application themes
   protected/                containing protected application files
      yiic                   yiic command line script for Unix/Linux
      yiic.bat               yiic command line script for Windows
      yiic.php               yiic command line PHP script
      commands/              containing customized 'yiic' commands
         shell/              containing customized 'yiic shell' commands
      components/            containing reusable user components
         Controller.php      the base class for all controller classes
         UserIdentity.php    the 'UserIdentity' class used for authentication
      config/                containing configuration files
         console.php         the console application configuration
         main.php            the Web application configuration
         test.php            the configuration for the functional tests
      controllers/           containing controller class files
         SiteController.php  the default controller class
      data/                  containing the sample database
         schema.mysql.sql    the DB schema for the sample MySQL database
         schema.sqlite.sql   the DB schema for the sample SQLite database
         testdrive.db        the sample SQLite database file
      extensions/            containing third-party extensions
      messages/              containing translated messages
      models/                containing model class files
         LoginForm.php       the form model for 'login' action
         ContactForm.php     the form model for 'contact' action
      runtime/               containing temporarily generated files
      tests/                 containing test scripts
      views/                 containing controller view and layout files
         layouts/            containing layout view files
            main.php         the base layout shared by all pages
            column1.php      the layout for pages using a single column
            column2.php      the layout for pages using two columns
         site/               containing view files for the 'site' controller
            pages/           containing "static" pages
               about.php     the view for the "about" page
            contact.php      the view for 'contact' action
            error.php        the view for 'error' action (displaying external errors)
            index.php        the view for 'index' action
            login.php        the view for 'login' action
~~~

Application generator described above also supports creation of files needed
by Git version control system. The following command would create necessary
`.gitignore` (e.g. content of the `assets` and `runtime` shouldn't be tracked)
and `.gitkeep` (forces tracking of initially empty but important directories)
files:

~~~
% YiiRoot/framework/yiic webapp WebRoot/testdrive git
~~~

Another supported VCS is Mercurial: pass the `hg` value as third parameter in
case you're using this VCS. This feature is available since version 1.1.11.

Connecting to Database
----------------------

Most Web applications are backed by databases. Our test-drive application
is not an exception. To use a database, we need to tell the
application how to connect to it. This is done in the application
configuration file `WebRoot/testdrive/protected/config/main.php`, highlighted as follows,

~~~
[php]
return array(
	......
	'components'=>array(
		......
		'db'=>array(
			'connectionString'=>'sqlite:protected/data/testdrive.db',
		),
	),
	......
);
~~~

The above code instructs Yii that the application should connect to the SQLite database
`WebRoot/testdrive/protected/data/testdrive.db` when needed. Note that the SQLite database
is already included in the skeleton application that we just generated. The database
contains only a single table named `tbl_user`:

~~~
[sql]
CREATE TABLE tbl_user (
	id INTEGER NOT NULL PRIMARY KEY AUTOINCREMENT,
	username VARCHAR(128) NOT NULL,
	password VARCHAR(128) NOT NULL,
	email VARCHAR(128) NOT NULL
);
~~~

If you want to try a MySQL database instead, you may use the included MySQL
schema file `WebRoot/testdrive/protected/data/schema.mysql.sql` to create the database.

> Note: To use Yii's database feature, we need to enable the PHP PDO extension
and the driver-specific PDO extension. For the test-drive application, we
need to turn on both the `php_pdo` and `php_pdo_sqlite` extensions.


Implementing CRUD Operations
----------------------------

Now comes the fun part. We would like to implement CRUD (create, read,
update and delete) operations for the `tbl_user` table we just created. This is
also commonly needed in practical applications. Instead of taking the trouble
to write the actual code, we will use `Gii` -- a powerful Web-based code generator.

> Info: Gii has been available since version 1.1.2. Before that, we could use the aforementioned `yiic` tool to accomplish the same goal. For more details, please refer to [Implementing CRUD Operations with yiic shell](/doc/guide/quickstart.first-app-yiic).


### Configuring Gii

In order to use Gii, we first need to edit the file `WebRoot/testdrive/protected/config/main.php`, which is known as the [application configuration](/doc/guide/basics.application#application-configuration) file:

~~~
[php]
return array(
	......
	'import'=>array(
		'application.models.*',
		'application.components.*',
	),

	'modules'=>array(
		'gii'=>array(
			'class'=>'system.gii.GiiModule',
			'password'=>'pick up a password here',
		),
	),
);
~~~

Then, visit the URL `http://hostname/testdrive/index.php?r=gii`. We will be prompted for a password, which should be the one that we just entered in the above application configuration.

### Generating the User Model

After login, click on the link `Model Generator`. This will bring us to the following model generation page,

![Model Generator](gii-model.png)

In the `Table Name` field, enter `tbl_user`. In the `Model Class` field, enter `User`. Then press the `Preview` button. This will show us the new code file to be generated. Now press the `Generate` button. A new file named `User.php` will be generated under `protected/models`. As we will describe later in this guide, this `User` model class allows us to talk to the underlying database `tbl_user` table in an object-oriented fashion.

### Generating CRUD Code

After creating the model class file, we will generate the code that implements the CRUD operations about the user data. We choose the `Crud Generator` in Gii, shown as follows,

![CRUD Generator](gii-crud.png)

In the `Model Class` field, enter `User`. In the `Controller ID` field, enter `user` (in lower case). Now press the `Preview` button followed by the `Generate` button. We are done with the CRUD code generation.

### Accessing CRUD Pages

Let's enjoy our work by browsing the following URL:

~~~
http://hostname/testdrive/index.php?r=user
~~~

This will display a list of user entries in the `tbl_user` table.

Click the `Create User` button on the page. We will be brought to the login
page if we have not logged in before. After logging in, we see
an input form that allows us to add a new user entry. Complete the form and
click the `Create` button. If there is any input error, a nice error
prompt will show up which prevents us from saving the input. Back on the
user list page, we should see the newly added user appearing in the list.

Repeat the above steps to add more users. Notice that the user list page
will automatically paginate the user entries if there are too many to be
displayed in one page.

If we login as an administrator using `admin/admin`, we can view the user
admin page with the following URL:

~~~
http://hostname/testdrive/index.php?r=user/admin
~~~

This will show us the user entries in a nice tabular format. We can click on the table
header cells to sort the corresponding columns. We can click on the buttons
on each row of data to view, update or delete the corresponding row of data.
We can browse different pages. We can also filter and search to look for
the data we are interested in.

All these nice features come without requiring us to write a single line
of code!

![User admin page](first-app6.png)

![Create new user page](first-app7.png)




